Visual inspection: upon visual inspection of the returned blocker, it can be seen that the bottom of the blocker has heavy, asymmetrical rod indentations.A review of the device history was performed and there were no relevant manufacturing issues identified as all units met stryker specifications.A review of the complaint history records was performed and there were no similar complaints identified.Per surgical technique: once the correction procedures have been carried out and the spine is fixed in a satisfactory position, the final tightening of the blockers is performed.To final tighten; use the anti-torque key and the torque wrench: step 1: place the anti-torque key over the screw head.Step 2: place the torque wrench through the anti-torque key until it is guided into the blocker.Step 3: line up the two arrows to achieve the final tightening torque of 8nm.The torque wrench indicates the optimal torque force that must be applied to the implant for final tightening.Note: do not exceed 8nm during final tightening.The anti-torque key must be used for final tightening.The anti-torque key performs two key functions: allows the torque wrench to align with the tightening axis and helps to maximize the torque needed to lock the implant assembly.Loosening of spinal fixation implants can occur.Early mechanical loosening may result from inadequate initial fixation, latent infection, premature loading of the prosthesis, or trauma.Late loosening may result from trauma, infection, biological complications or mechanical problems,with the subsequent possibility of bone erosion, migration and/or pain.While the expected life of spinal implant components is difficult to estimate, it is finite.These components are made of foreign materials which are placed within the body for the potential fusion of the spine and reduction of pain.However, due to the many biological, mechanical and physicochemical factors which affect these devices but cannot be evaluated in vivo, the components cannot be expected to indefinitely withstand the activity level and loads of normal healthy bone.As the rods were not seated horizontally into the tulip and the blockers were not torqued to the recommended 8nm, it is likely that the uneven force distribution created instability in the construct.This could have caused the rod to slip/migrate from the tulip.It is also possible that the instability in the construct may have also contributed to the migration of the s1 screws, along with the patients poor bone quality.
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